In the continuous quest to find cost-effective methods to
explore the planets, NASA engineers have risen to the occasion by
developing a variety of new balloon methods inspired by
centuries-old, solar-heated hot-air balloons, as well as by
conventional helium light-gas balloons.

For NASA, balloons are of considerable interest as a means
of lowering spacecraft to a planet's surface, delivering
instruments to various altitudes and performing aerial
photography and other forms of remote-sensing science. Balloons
can also potentially conduct explorations faster and cover
greater distances than conventional ground-based planetary
explorers.

"Solar-heated balloons can descend more slowly than heavier
parachutes to drop off a payload, and yet they can rise again
after the drop-off. They offer us bonus science because they can
take off repeatedly during daylight hours, and land in hard-to-reach
terrain," said Jack Jones, technical monitor for balloon
activities at NASA's Jet Propulsion Laboratory in Pasadena,
Calif. "Our inspiration comes from the centuries-old
Montgolfiere balloons named after the two French Montgolfier
brothers who flew the first hot-air balloon by burning a pile of
wool and old shoes in 1783."

Other balloons use ammonia, which evaporates with solar
heat, and causes inflation of the balloon. Helium balloons can
also potentially be used and can fly for several weeks, which is
much longer than the one-day flights of the solar heated
balloons. The helium balloons tend to be heavier and more
complicated since they must be stronger and carry their own high-
pressure compressed gas cylinders for in-flight filling. All of
these balloons can be used to explore the atmosphere and large
areas of a planet's surface. "Thus far, most of our work has
concentrated on balloon deployment testing in Earth's upper
atmosphere, which simulates deployment in the cold, thin
atmosphere like that of Mars," said Jones.

Engineers in JPL's Mechanical Systems Engineering and
Research Division are also developing a variety of aerovehicles
to explore other solar system bodies, such as Venus, Saturn's
moon Titan, and the outer planets (Jupiter, Saturn, Uranus and
Neptune). The aerovehicles include balloons designed to enable
scientific exploration by either hovering over or soft landing on
planetary bodies. Another class of inflatable drag devices,
called ballutes, may someday be used to decelerate a spacecraft's
speed to allow insertion into orbit.

In addition to solar-heated balloons, hot-gas balloons also
look promising for Jupiter and Saturn, while balloons on Uranus
and Neptune can capture light, high-altitude gas to float in the
heavier atmosphere below the methane clouds. These balloons may
be able to study the gas planets' internal energy sources and
atmosphere.

On Venus, a combination helium-and-water or steam balloon
may be used to make repeated descents to the hot, scalding
surface with re-ascents to the upper, cooler clouds and perhaps
help define what caused Earth's twin to have such a hot,
greenhouse atmosphere. And on Titan, a helium-filled "aerover"
may be able to fly like a blimp and then land as an amphibious
rover to explore that moon's strange frozen surface and liquid
hydrocarbon lakes or seas.

JPL's planetary balloon activities are funded by the NASA
Mars Exploration Office and the NASA Cross Enterprise Program.
Managed for NASA by the California Institute of Technology in
Pasadena, JPL is the lead U.S. center for robotic exploration of
the solar system.

#####

3/26/2001 CM
#2001-067

NOTE TO EDITORS: Live satellite interviews are available with
Jack Jones, technical monitor for balloon activities at JPL on
Wed., March 28. To book time for this interview, call Jack
Dawson at 818-354-0040 or e-mail Jack at
jack.b.dawson@jpl.nasa.gov .

A video file with animation and B-roll will accompany this
release and is scheduled to air on NASA Television on March 27,
28, 29 at noon, 3 p.m., 6 p.m., 9 p.m. and midnight EST.
NASA Television is available at GE-2, Transponder 9C at 85
degrees West longitude, with vertical polarization. Frequency is
on 3880.0 megahertz with audio on 6.8 megahertz.